A variety of packages, including dispensing packages or containers, have been developed for personal care products such as shampoo, lotions, etc., as well as for other fluid materials. One type of closure for these kinds of containers typically has a bistable hinge structure connecting a lid to a base mounted over the container opening. The hinge structure has a snap-action biasing force which maintains the lid in a selected closed or open position.
A hinge structure for a closure disclosed in U.S. Pat. No. 4,403,712 has a single, main geometric axis hinge and has two webs each defined by two hinges which diverge on either side of the web.
A snap-action hinge structure with significant improved operating characteristics is a dual axis hinge structure disclosed in the U.S. Pat. No. 5,642,824. The hinge structure is of the type that includes a web having a narrow central portion between two wider ends. An arcuate hinge connects a closure base to the web along one side of the web between the hinge ends. An arcuate hinge connects the closure lid to the web along another side of the web between the hinge ends. The hinge structure includes at least one abutment surface located so that when the lid is in the closed position, the abutment surface extends adjacent the web central portion from near one of the hinges toward the other hinge. During the closing and opening of the lid, the abutment surface is contacted by the web central portion whereby the position of the web is controlled.
Another snap-action, dual axis hinge structure with an improved design is disclosed in U.S. Pat. No. 6,321,923. The hinge structure includes a web having a narrow, central portion between two wider ends which each defines a lateral edge. The hinge structure also includes a first arcuate hinge connecting the closure lid to the web along one side of the web between the lateral edges. The hinge structure includes another arcuate hinge connecting the closure base to the web along another side of the web between the lateral edges. The web has two spaced-apart regions of reduced thickness. The reduced thickness regions are located between, and are reduced in thickness relative to, the arcuate hinges. Each reduced thickness region extends to one of the adjacent, lateral edges. The hinge structure has enhanced resistance to fracture or failure. The improved resistance to failure results from a configuration that provides a particular distribution of stress along the outer or lateral edges of the hinge structure and a concomitant reduction in stress at the points where the outer edges of the hinge structure are connected to the two members, such as a closure body and a closure lid. Although such a hinge structure functions with improved operating characteristics, there are some applications, such as those involving a large number of opening and closing cycles, in which the dual axis hinge structure (as well as other biased hinge structures or bistable, snap-action hinge structures) may be more likely to fail or break.
It is believed that in a snap-action hinge structure which includes two or more hinges and includes a web having at least one wide end, the stresses are greater and/or are unevenly distributed, along the lateral edges of the web and at the corners of the web where each of the hinges terminates. Failure or fracture of such hinge structures is typically initiated at those regions where a lateral edge of the hinge structure web connects with the closure body and/or lid at the end of each hinge.
Thus, it would be desirable to provide an improved snap-action hinge design in which the stresses in the hinge structure could be more carefully controlled. In particular, it would be beneficial if such an improved design could provide a lower stress, or reduced stress concentration, at each opposite end of the hinge structure.
It would be especially desirable to provide a hinge structure which would have reduced stresses at the opposite ends of each of two hinges in a dual axis hinge structure connecting a closure body and lid.
It would be beneficial if such an improved hinge structure design could also optionally accommodate a design that permits the hinge structure to provide the desired opening and closing angle range for the lid. A hinge structure with such a capability can provide performance features that are desirable in particular applications.
Also, it would be desirable if such an improved hinge structure could be readily incorporated in a closure that would accommodate efficient, high quality, large volume manufacturing techniques with a reduced product reject rate.
Further, such an improved hinge structure should advantageously accommodate its use in closures with a variety of conventional containers having a variety of conventional container finishes, such as conventional threaded or snap-fit attachment configurations.
The present invention provides an improved hinge structure which can accommodate designs having one or more of the above-discussed benefits and features.